The present invention relates to semiconductor acceleration sensors and specifically to such sensors which employ the piezoresistive effect of single crystal silicon.
Semiconductor accelerometers are particularly useful for biomedical, aerospace and automotive applications. The basic semiconductor accelerometer of the prior art comprises a cantilevered silicon beam and mass with a resistor implanted on the beam which changes its value with acceleration due to the stress induced in the beam. A second resistor may be included on the unstressed portion of the structure for temperature compensation and the two resistors connected together to form a half-bridge circuit. One such device is described by L. Roylance and J. Angell in an article entitled "A Batch-Fabricated Silicon Accelerometer", I.E.E.E. Transactions on Electron Devices, vol. ED-26, No. 12, December 1979, pp. 1911-1917.
Another prior accelerometer includes a double-mass and employs the tensile and compressive loading of resistors simultaneously. However, this results in an asymmetric response, and metallization on the flexible portion of the device induces thermal deformation which contributes to nonlinearity and accuracy.
There is thus a need for a low-cost, accurate and sensitive semiconductor accelerometer which can be mass-produced using standard planar processing techniques.